1. Field of the Invention
The present invention is directed to a semiconductor laser chip, whereby a laser-active semiconductor structure is arranged in an optical resonator.
2. Description of the Relate Art
Such laser chips are disclosed, for example, by the publications U.S. Pat. No. 5,016,252, Japanese Published Application 2-71574 and Japanese Published Application 61-247084. These disclose laser diode chips wherein an n-conductive cover layer, an active layer and a p-conductive cover layer are successively applied on a semiconductor substrate.
Semiconductor laser chips of this type are made of the material systems InAlGaAs or InAlGaP on a GaAs substrate, InAlGaAsP on an InP substrate or InAlGaN on a sapphire or SiC substrate as edge which are referred to as vertical cavity surface emitting lasers (VCSEL).
An object of the present invention is to provide a semiconductor laser chip that exhibits enhanced efficiency and an enhanced output power compared to the Prior Art.
This object and others are achieved by semiconductor laser chips having a laser-active semiconductor structure is arranged in an optical resonator, two or more series-connected, laser-active pn-junctions whose forward directions are isodirected introduced into the same resonator of the semiconductor laser chip, the laser-active pn-junctions contain quantum wells for the charge carrier recombination, a pn-junction whose forward direction is directed opposite the forward direction of the laser-active pn-junctions is respectively arranged between two laser-active pn-junctions, this reverse-poled pn-junction is located in semiconductor material having a larger band gap than that of the semiconductor material of the laser-active pn-junctions, and the laser-active pn-junctions are located in a wave-guiding zone.
In another embodiment, the emitting semiconductor laser chip has a laser-active semiconductor structure arranged in an optical resonator, two or more series-connected, laser-active pn-junctions whose forward directions are isodirected are introduced into one and the same resonator of the semiconductor laser chip, the laser-active pn-junctions contain quantum wells for the charge carrier recombination, a pn-junction whose forward direction is directed opposite the forward direction of the laser-active pn-junctions is respectively arranged between two laser-active pn-junctions, this reverse-poled pn-junction is located in semiconductor material having a larger band gap than that of the semiconductor material of the laser-active pn-junctions, and the quantum wells of the laser-active pn-junctions are located in the bellies and the reverse-poled pn-junction is located in the node or, respectively, in the nodes of the standing wave field generated in the semiconductor chip.
According to the invention two or more series-connected, laser-active pn-junctions are introduced into the same resonator of the semiconductor laser chip, the forward directions of the pn-junctions being isodirected. The laser-active pn-junctions contain quantum wells for the charge carrier recombination. A pn-junction whose forward direction is opposite to the forward direction of the laser-active pn-junctions, that is thus reverse-poled compared to the forward direction of the semiconductor laser chip, is arranged between the pn-junctions. The reverse-poled pn-junction or junctions are located in a semiconductor material having a greater band gap than the semiconductor material of the laser-active pn-junctions.
Given an edge-emitting semiconductor laser chip, the laser-active pn-junctions are located in a wave-guiding zone. Given vertically emitting semiconductor laser chips (VCSELs), the quantum wells of the laser-active pn-junctions lie in the bellies and the reverse-poled pn-junction or, respectively, the reverse-poled pn-junctions lie in the node or nodes of the standing wave field generated in the semiconductor laser chip.
Advantageously, the spacing between two successive laser-active pn-junctions amounts to less than 2 xcexcm.